Substance addiction is a chronic, relapsing disease characterized by a loss of control over drug use, compulsive drug seeking and craving for a substance, use that persists despite negative consequences, and physical and/or psychological dependence on the substance. Substance addiction typically follows a course of tolerance, withdrawal, compulsive drug taking behavior, drug seeking behavior, and relapse. Addictive substances include alcohol, caffeine, nicotine, cannabis (marijuana) and cannabis derivatives, opiates and other morphine-like opioid agonists such as heroin, phencyclidine and phencyclidine-like compounds, sedative ipnotics such as benzodiazepines and barbiturates and psychostimulants such as cocaine, amphetamines and amphetamine-related drugs such as dextroamphetamine and methylamphetamine. Substance abuse and addiction are public health issues. They have significant social and economic impact on both the addict and society by playing a major role in violent crime and the spread of infectious diseases.
According to the World Health Organization, an estimated 13 million people abuse opiates worldwide, including 9 million heroin addicts. More than 25% of opiate abusers die from suicide, homicide, or an infectious disease, such as HIV and hepatitis, within 10-20 years of becoming addicted. Tolerance and physical dependence can develop within two to three days.
The goals for treatment of opiate addiction, as with other types of substance addictions, are to discontinue the use of the opiate while minimizing painful withdrawal symptoms and preventing relapse. Current treatments involve replacing the addictive drug with a substitution of an opioid receptor agonist or mixed agonist/antagonist. An alternative approach consists of the use of an opioid receptor antagonist to block the effect of the agonist.
Alcohol is one of the most commonly abused substances at a global level. Alcoholism leads to serious liver and cardiovascular disease and generates dependence resulting in severe mental disorders, social problems and adverse consequences including the division of families, tragic accidents and the reduction of work performance. According to the WHO, alcohol consumption is responsible for 20-30% of oesophageal and liver cancer, liver cirrhosis, homicides, epilepsy, and motor vehicle accidents world wide. Globally, alcohol abuse leads to about 1.8 million deaths per year. Compulsive behavior towards the consumption of alcohol is a core symptom of the disorder. In recent years several approaches have been investigated to help alcoholic patients to not only control alcohol drinking but also alcohol cravings and relapse.
Several classes of medications such as naltrexone, acamprosate, ondansetron, disulfiram, gamma hydroxybutyrate (GHB), and topiramate have been tested for their potential therapeutic effect on alcohol abuse. Naltrexone, acamprosate, and disulfiram have been proven to be of a certain utility and approved for the treatment of alcoholism. Among these medications, the non-selective opioid antagonist naltrexone is currently considered the pharmacological gold standard.
The National Institute on Drug Abuse estimates that 72 million Americans, about one-third of the population, have tried marijuana. Acute effects of marijuana use include memory and learning problems, distorted perception, difficulty problem solving, loss of coordination, and increased heart rate. Long term abuse can cause the same respiratory problems observed in tobacco smokers, such as daily cough, phlegm production, increased risk of lung infections, and an increased chance of developing cancer of the head, neck and lungs. Depression, anxiety, and job-related problems have been associated with marijuana use. Long term marijuana use can result in addiction with compulsive use that interferes with daily activities. Cravings and withdrawal symptoms, such as irritability, increased aggression, sleeplessness, and anxiety make it difficult for addicts to stop using marijuana.
Psychostimulants, such as cocaine and amphetamines, cause euphoria, increased alertness, and increased physical capacity in humans. These substances first increase dopamine transmission, but long term drug usage results in a reduction of dopamine activity, leading to dysregulation of the brain reward system and dysporia. The WHO estimates 33 million people around the world abuse amphetamines.
Chronic cocaine abuse can result in hyperstimulation, tachycardia, hypertension, mydriasis, muscle twitching, sleeplessness, extreme nervousness, hallucinations, paranoia, aggressive behavior, and depression. Cocaine overdose may lead to tremors, convulsions, delirium, and death resulting from heart arrhythmias and cardiovascular failure. Desipramine, amantadine and bromocriptine have been shown to decrease cocaine withdrawal symptoms.
Amphetamine withdrawal symptoms include EEG changes, fatigue, and mental depression. Tolerance develops over time and may be associated with tachycardia, auditory and visual hallucinations, delusions, anxiety reactions, paranoid psychosis, exhaustion, confusion, memory loss, and prolonged depression with suicidal tendencies. Current treatments for amphetamine addiction include phenothiazines, haloperidol, and chlorpromazine for hallucinations.